2007 Saturn Aura Timing chain

It's not impossible but it isn't terribly easy. You'll run into some things you probably haven't seen before, like hydraulic tensioners. Your engine uses multiple tensioning devices so you shouldn't have a rattle from the timing chain. Try banging on the catalytic converter with a rubber hammer first. If you hear the rattle, the substrate has broken loose. That's more common than timing chain rattles.

Years ago a stretched timing chain did cause low power because it caused late camshaft and valve timing. A camshaft that is one or two degrees late will give you lots of low-end power and a loss of high-end power. They do that for motor homes so they can get going at stop signs. Today's engines use spring-loaded tensioners that may also be fed with pressurized engine oil.

Whether your engine has a power loss due to a stretched chain depends on where that tensioner takes up the slack. If it's on the side where the crankshaft sprocket pulls on the chain and camshaft sprocket, the tensioner should keep the valve timing correct. Usually those devices are on the less-stressed side where the chain has just left the crank sprocket. It won't keep the valve timing correct but it will be easier to adjust the slack out of the chain.

Late valve timing won't cause a rough idle. The idle quality will be unusually smooth, but with less throttle response and less power.

Bang on it with a rubber hammer. If the substrate is loose, you'll hear it rattle.

And don't overlook a loose heat shield too.